An odd theory that has floated around for years is that JFK's driver on Nov. 22, 1963, William Greer, fired the fatal shot. The legendary Zapruder film, showing Greer's hands on the steering wheel, discredits the theory.

The idea of a second shooter on Dealy Plaza in Dallas has been floated since Nov. 22, 1963. Multiple theories have focused on a woman in a shawl, a man with an umbrella and a random person standing on the grassy knoll.

A convoluted theory takes JFK's assassination through New Orleans and ties it to the mafia, including Gulf Coast mafia figure Carlos Marcello (pictured) and businessman Clay Shaw. Oliver Stone's movie "JFK" centered on this theory. Shaw went on trial for his alleged role in Kennedy's death, but was acquitted.

Conspiracy theorists floated the idea that Vice President Lyndon B. Johnson of Texas was involved from the start in having President Kennedy assassinated. These theories seem based on Johnson's long desire to be president and the fact that Kennedy died in Dallas. Multiple investigations found no proof to back up the ideas.

Conspiracy theorists floated the idea that Vice President Lyndon B. Johnson of Texas was involved from the start in having President Kennedy assassinated. These theories seem based on Johnson's long desire

There was an initial suspicion that Soviet Premier Nikita Khrushchev (pictured with President Kennedy) ordered the hit on JFK because he had to back down during the Cuban Missile Crisis. The Warren Commission brushed this one off. "The committee believes, on the basis of the evidence available to it, that the Soviet Government was not involved in the assassination of President Kennedy"

A far-fetched theory is that Jackie Kennedy killed her own husband. The idea behind this one is twisted and requires a creative reading of history and the evidence from the scene. Suffice to say, there's never been any actual evidence that she was involved in the killing.

Accidents happen, even around presidents. Some conspiracy theorists believe Secret Service Agent George Hickey, riding in the follow-up car, accidentally shot the president. This theory has been repeatedly debunked.

Was JFK, with his pledge to go to the moon, getting too close to discovering intelligent life in outer space? And, did they not want to be found out? This one seems like it came out of the "X-Files" TV show.

Was JFK, with his pledge to go to the moon, getting too close to discovering intelligent life in outer space? And, did they not want to be found out? This one seems like it came out of the "X-Files" TV

Follow this conspiracy theory: John F. Kennedy had Marilyn Monroe killed after having an affair with her. Joe DiMaggio, the New York Yankee great, was Monroe's ex-husband and angry over her death. He conspired with the mafia to have Kennedy killed. There's never been any evidence that Kennedy had anything to do with Monroe's death nor any evidence that DiMaggio played a role in Kennedy's demise.

Another favorite boogeyman of conspiracy theorists. In relation to JFK's death, conspiracy theorists have floated the idea that the spy agency hired Lee Harvey Oswald to do the deed. The Warren Commission found no evidence to support this idea.

Another favorite boogeyman of conspiracy theorists. In relation to JFK's death, conspiracy theorists have floated the idea that the spy agency hired Lee Harvey Oswald to do the deed. The Warren Commission

Here's a theory that starts with one of President Kennedy's own actions - the signing of Executive Order 11110. The order reigned in some of the Federal Reserve's power, the theory goes, angering the billionaire class who felt it necessary to eliminate Kennedy.

There are several conspiracy theories involving Cubans and Fidel Castro connected to President Kennedy's death. One is that Castro was upset about the Bay of Pigs invasion in 1961 and sought revenge. The other is that veterans of the invasion were upset with Kennedy over the mission's failure and had him killed in retaliation.

There are several conspiracy theories involving Cubans and Fidel Castro connected to President Kennedy's death. One is that Castro was upset about the Bay of Pigs invasion in 1961 and sought revenge. The

A favorite boogeyman of conspiracy theorists for all occasions, the Illuminati, long believed to be a shadowy group that runs the world and eliminates it's enemies, had JFK killed. And, what would a list of conspiracy theories be without them.

Lee Harvey Oswald, who once defected to the Soviet Union before returning to the United States, was pegged as John F. Kennedy's killer. But, theories abound as to his motives and whether he worked with anyone else. The Warren Commission, which examined the assassination to almost no one's satisfaction, concluded that Oswald acted alone.

John F. Kennedy was shot and killed Nov. 23, 1963 in Dallas and buried in Arlington National Cemetery. But, some people believe it was all a hoax. There's a theory that Kennedy lived (and may still be alive). There's nothing credible to back this concept, but hours can be spent running down the rabbit hole of theories and websites dedicated to this idea.

The Fort Worth-native was a mainstay on late-night radio show "Coast to Coast AM" and the "Alex Jones' Infowars" program.

In late June Marrs posted a note on his official website that said he was suspending work on the site to address his health issues.

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Newly released documents by the U.S. government may lend some support to the conspiracy claim that Russia was behind the assassination of John F. Kennedy. Josh King has the story (@abridgetoland).

Media: Buzz60

According to his online biography, Marrs was a former Fort Worth Star-Telegram staffer starting in 1968 and was a police reporter and general assignments reporter. After a stint serving in the Army in Vietnam he came back home and began writing about military and aerospace technology.

His 1989 book "Crossfire: The Plot That Killed Kennedy" was a New York Times Paperback Non-Fiction Best Seller and became a basis for the Oliver Stone film "JFK" in 1991. He served as a chief consultant for the film.

He had taught a course on the 1963 killing of the president at the University of Texas at Arlington, starting in 1976. He retired in 2007.

Marrs could usually be found in Dealey Plaza in Dallas on the anniversary of the assassination every November 22, talking to fans and speaking with the media in front of the so-called Grassy Knoll, ground zero for conspiracy theorists.

His work on 9/11 dealt with what he called an inconsistent public story on the terrorist attacks.

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Other Marrs books included "Psi Spies," "Alien Agenda," "Rule by Secrecy," "The War on Freedom," "The Terror Conspiracy" and "The Rise of the Fourth Reich", all of which were met with praise by a devoted community of skeptics if not mainstream audiences.